Process for the purification of leachijktg solution s and the recovery oei



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Filed Nov. 17, 1923 Snom/1to1 RCHER E. WHEELER.

L; N, l' i. u "HOM Patenten no, lat-afd UNlTE STATES lfitld PATENTOFFICE.

ARCHER E. WHEELER, OF SCARSDALE, NEVI YORK.

PROCESS FOR THE IPURIFICATION OF LEACEING SLU'lOJ-S AND THE RECOVERY OFACIDS 0R DSSOLVING AGENTS.

Application filed November 17, 1323.

This invention relates to improvements in the method ot purifyingleaching solutions and the recovery ot acids or dissolving agents forreuse in leaching out the desired constituents from tinely coinminutedore.

ln any commercial leaching process, the dissolving agent, besides takinginto solution the valuable soluble constituent in t-he ore or materialbeing treated, also dissolves varying amounts o'l' other constituentswhich are ot no value to the operator. 'lhese may be referred to asimpurities. Vlhese impurities gradually accumulate in the solutionunless an etlort is made to remove them and may nally result in a foulsolution., in which the impurities hinder the recovery ot the desiredvaluable element.

For example, in the leaching ot copper ores by sulphuric acid, the acidnot only takes copper into solution, but also varying amounts of lime,magnesia, iron, alumina, etc. The accumulation oit these impurities maycause trouble. For example, the presence of iron in a solution Which isbeing electrolyzed to recover the copper, has a tremendous detrimentalaffect on ampere eiliciency. ln tact there is a point ot iron content atwhich ampere efficiency would drop almost to zero. Again, the presenceot large quantities ot alumina has a marked effect on the dissolvingpower et a leaching solution, and too large quantities ot this elementwill result in low copper extractions. To operate etliciently care mustbe talen to rid the solution oit the accumulation ot those impuritieswhich cause trouble. One common though wasteful prior method is todiscard enough solution trom time to time or continuously, to removefrom the solution the input of objectionable impurities.

llillien an acid solution containing consider able quantities of theimpurities.. such as iron and alumina, is neutralized by furtheradditions oi? ore and agitated for a sufficient length ot time, the ironand alumina are precipitated to a greater or less extent. Attempts havebeen made to utilize this tact to purity leachingv solutions, but asuccessful method so tar as l am avvare has never heretofore beendeveloped. Precipitation has been effected, but at the expense ot a lossof copper in the excess ore necessary to be added to cause the reactionto proceed, and the precipitated iron and alumina Were not pre- SeralNo. 675,285.

vented 'from going back into solution in some further step in th-eprocess.

My improved process overcomes practical diiiiculties heretoforeencountered and enables me to effectively and economically purityleaching solutions Without loss of the copper or other desiredconstituent in the excess ore which is added in carrying out the processand also enables me to recover the acid or other desired agent forimmediate reuse in dissolving the required constituent trom the ore.

ln carrying out my method, I add an eX- of comminuted ore to the acidimpurityladen solution and agitato this mixture so as to precipitate theiron, aluminum salts and other impurities.

I then separate the finer particles ot ore together with the iron andalumina from the coarser particles oi. ore before subjecting the ore toany 'further treatment which Would dissolve out the requiredconstituent. lVhen a given ore of copper is treated or leached, thesolution or" the finer particles is very much faster than is out ol' thecoarser' particles; hence, the greater proportion of the required orvaluable constituent of the Ore is in the larger particles which havebeen separated trom the smaller particles and impurities.

There is also another method of carrying out my process, in which theore is added to neutralize the solution and precipitate ther impurities,is all or substantially all, coarser than the precipitate orprecipitated particles ot impurities. In this case the classilicationfollowing the neutralizing agitation results in the separation of theprecipitated impurities alone, or these impurities mixed With only asmall amount of fine ore or precipitating material from the coarserparticles oi the ore or precipitatimgmaterial.

An example oit my method is described below with reference to theaccon'ipanying dia-- grammatic drawing forming part et thisspecilication.

Referring to the drawing, o represents feed launder in Which the acidimpurityladen solution, mixed with an excess oi' the ore, is fed througha series of agitators, c and d. These agitators are of suiilcient volumeto give a time of agitation necessary to produce the requiredprecipitation. The discharge from the agitator Z goes to classifier c.This discharge consists of a neutral solution containing as solids insuspension, ore which has only partly been depleted oill its coppercontent, and also a precipitate ot iron and aluminum salts, and anyother impurities Which Will precipitate under these conditions. Theclassifier e is set to deliver a sand product of say, plus 100 mesh Atothe agitator r/.

wWhen a given ore ot copper` is dissolved, the solution ot' the copperout ot' the liner particles of ore is very much laster than it is out ofthe coarsor r'iarticles. For this reason, the lgreatest part ot theexcess copper which Wasted to the agritators o, o and. u7- will be'Found in the coarser sand discharged trom the classil'ier c and vthissand dizrichai'ge is oelivered 'to a series oil acid zuritatori-i y, l1,and 'i in which the remaining.; copper is entirelv remo ved.

All the tine particles oiP4 ore trom which the copper has been ren'iovedand along Awith them the flocculent 'precipitate ot `iron and alumininnand other salts e carried over in the overflow 7c olf the clin iif-r andare delivered to a thickener o; other means oi' separating' the solidsV.troni the liquid. clear neutral solution is returned to the tem by apipe Z and the solids are pumped 'from the bottom of the tank through apipe m and washed in a suitable washing apparatus. This solid containsline barren ore and the precipitated iron and alumina and otherprecipitated salts.

It is clear that any impurities which aro taken into solution. serve asconsumers o'l acid which on discharging the solution as heretofore donemeans a direct loss o't' acid and therefore resulting` high costs.

The precipitation ot the iron and alumina, and perhaps of sonic othersalts, results in the release ot all or a part of the acid ordissolving,` agent which Was in combination with the iron and alumina.This released acid or dissolv'iiigv agent imn'iediatoly dissolves copper'from the orc, thus recover-iin; a part ot the acid or dissolving agentwhich would otherwise be lost or discarded.

Thus my method accornlishes the el iinination of iron and alumina tronithe original solution without losing the copper which it was necessarylo add in enc to produce the `given reaction; removes the precipitatmlini-- purities from the solution without ojivinu them a chance to beredisfiolvcd and recm'e for reuse pai f oi the acid or dissolving uncutwhich in prior methods would 'be lost.

Thilo in the above described example of my process I have set- `lorththat the iron., alumina or other impurities are precipitated by adding'an excess o1p4 ore, it is to be understood that I may bring about thisaction by bringing the solution `to such a condition either chemicallyor physically, or both chemically and vlohysically that the desiredprecipitation takes place. .Instead oit using fore,

I may use any other suitable substance or The monaco' substancescontaining different size particles in which case I Will separate tnoprecipitate and the liner particles ot the precipitating agent from thecoarser particles before any tui-ther operation isv performed which`vill redissolve the precipitate.

l.While I have described with great particularity the treatment of aspecilic ore With the use of a speeiiic acid or dissolving agent andhave recited the steps in my process in a delinite sequence, it is to beunderstood that I ein not limited thereto and that the descrip tion anddrawings are to be construed in an illustrative rather than limiting`senso.

l. In the puriiication olf leaching solutions, the method which includesthe stepsr of adding a mass of particles of different sizes toneutralize the solution and to precipitate the impurities and separatingthe precipitate and finer particles from the coarser particles.

2. In the purification of .leaching` solutions, the method whichincludes adding a mass ot' ore particles approximately the same size butall largey than the precipitated particles of impurities, and separatingthe precipitated particles from the eoarser ore particles which containsoluble constituents and subjecting the co'arser ore particles tofurther treatment.

3. In the purification of leaching solutions used in the treatment torecover the valuable constituent from ores containing .iron and alumina,the method Which includes the steps of adding an excess of ore particlesoit different sizes to neutralize'the solution and cause theprecipitation of iron, alumina and other impurities, and separating` thesaid precipitate and liner particles of ore 'from the coarser particlesbefore subjecting the mixture to any treatment Which would `redissolvethe precipitated impurities.

4;. In the recovery and purilication of leaching solutions used in thetrcatnient of ores containing iron and alumina the method which consistsoit adding` an excess ot ore to the solution to render it neutral,agitating the mixture or otl'ierwise bringing the solution and ore orother precipitant into intimate contact Vto precipitate the iron andalumina and other impurities, subjecting` the Whole to the sizingoperation to physically separate the precipitated iron and alumina andother impurities .troni the coarser particles, dischargingtheprecipitated iron and alumina and other impurities, and then subgectinp;the coarser particles to further treat-ment.

5. In the recovery and purification of leaching solutions or dissolvingagents used in the treatment of ore containing iron and alumina, themethod which consists of adding an excess of ore to the solution torender it neutral, bringing the solution and ore into vintimate contactto lprecipitate the iron and alumina and other impurities, ischargingthe preclpltated iron and alumina together n'itli the liner {mrticlesand clarifying the solution and returning it to the system for reuse anddischarging the coarse particles to a receptacle for further treatment.

6. ln the recovery and purification of leaching solutions or dissolvingagents used in tlie treatment ot ores containing' iron and alumina, themetliod which includes the steps of adding an excess ot ore particles otdifei ent sizes to bring the solution to suoli connition that iron,alumina and other impi'lrities are precipitated, and tlicn separating`said precipitated impurities and the finer particles of theprecipitating agent iroin tlie coarser particles before subjecting themass to any treatment wliicli would redissolve the precipitate andsubsequently treating the coarser particles to recover the desiredconstituents.

7. In the purification of leaching` solutions the method which includesadding a mass of particles oi' different sizes 1out all or substantiallyall of larger size than the precipitated particles of impurities, andseparating tlie precipitated particles from the coarser particles whichcontain soluble constituents and subjecting the coarser particles tofurther treatment.

ln Witness whereof, I have hereunto signed my name.

ARCHER E. VHEELER.

